The results regarding changes in the content of vitamin D2 in dried mushroom are presented in Table 1. The fruit bodies of mushrooms after UVB irradiation for 30 min. were subjected to convection drying. The analysis of ergocalciferol content in non-irradiated dried mushrooms showed that cultivated mushrooms were totally devoid of vitamin D2 (data not show in Table 1). The most probable reason for lack of ergocalciferol in cultivated mushrooms is that they are cultivated and harvested in darkness or with artificial light. In fresh fruit bodies of mushrooms immediately after UVB irradiation vitamin D2 content was found to be 56.60 μg/g dry matter in the case of oyster and 29.33 μg/g dw in shiitake, and fresh white button mushrooms were characterized by the lowest content of the analyzed compound at the level of 13.10 μg/g dw despite the fact that it had the highest content of vitamin D2 precursor – ergosterol (Table 4). The difference between the content of vitamin D2 in button mushrooms and two other species is probably due to different structure of fruit bodies. Button mushroom which were used in the study had closed caps as they are preferred both for food processing and targeted direct sales. Therefore, UVB had limited access to the gills area. Many authors have reported that in the gills part is up to two times more ergosterol than in caps or stalks (Jasinghe and Perera, 2005 and Perera et al., 2003).